Dictionary

Body systems

Anatomy and the conditions of each body system, from the heart and lungs to the skin.

sickle cellA red blood cell bent into a stiff, curved crescent shape by an abnormal type of hemoglobin.

sickle cell anemiaAn inherited blood disorder in which abnormal hemoglobin makes red blood cells stiff and curved like a sickle.

sigmoidShaped like the letter S; most often short for the sigmoid colon, the S-shaped last part of the colon before the rectum.

sinusA hollow space in the body, most often one of the air-filled spaces in the skull bones around the nose.

sinus bradycardiaA regular heart rhythm that starts normally in the sinus node but runs slower than 60 beats per minute.

sinus rhythmA heart rhythm that starts in the sinoatrial node, the heart's natural pacemaker.

sinusitisInflammation of the lining of the sinuses, the air spaces around the nose.

skeletalHaving to do with the skeleton, the framework of bones that supports the body.

skeletal muscleMuscle attached to bones that a person moves by choice, such as the muscles of the arms and legs.

skin breakdownDamage that opens or wears away the skin, such as a pressure injury, skin tear or damage from moisture.

skin cancerCancer that starts in the cells of the skin.

skin turgorHow quickly a gently pinched fold of skin goes back to its normal position.

skullThe bony frame of the head, made up of the cranium around the brain and the bones of the face.

sleep apneaA sleep disorder in which breathing stops and starts again and again during sleep.

sloughSoft, moist dead tissue in a wound, usually yellow, tan, gray or green, that may be stringy or stuck to the wound bed.

small for gestational ageDescribes a newborn whose birth weight is below the 10th percentile for the number of weeks of pregnancy.

small intestineThe long, narrow part of the bowel between the stomach and the large intestine, where most digestion and absorption happen.

smooth muscleMuscle that works without conscious control and lines hollow organs such as the stomach, intestines, bladder, airways and blood vessels.

social isolationHaving little contact with other people, or being cut off from family, friends and community.

soft palateThe soft, muscular back part of the roof of the mouth, with no bone in it.

soft tissueThe body tissues that connect, support or surround other parts, such as muscle, fat, tendons, ligaments, blood vessels and nerves, but not bone.

soluteA substance, such as salt or sugar, that is dissolved in a liquid.

somaticRelating to the body, as opposed to the mind.

Somogyi effectA high morning blood glucose that follows a low blood glucose during the night.

spasmA sudden, involuntary tightening of a muscle or of the muscle in a hollow organ or tube.

spasticityMuscle stiffness and tightness that resists stretching, more strongly the faster a limb is moved.

spermThe male reproductive cell, which can join with an egg to start a pregnancy.

sphincterA ring of muscle that tightens to close an opening or passage in the body and relaxes to open it.

spina bifidaA birth defect in which the bones of the spine do not close completely around the spinal cord.

spinal cordThe long bundle of nerves that runs down through the backbone and carries messages between the brain and the body.

spinal cord injuryDamage to the spinal cord that disrupts signals between the brain and the body below the injury.

spinal nerveOne of the 31 pairs of nerves that branch from the spinal cord to carry signals to and from the body.

spleenAn organ in the upper left abdomen that filters the blood and helps fight infection.

splenomegalyEnlargement of the spleen.

spontaneous abortionThe loss of a pregnancy on its own, before the fetus can live outside the uterus, usually before 20 weeks; a miscarriage.

sprainA stretch or tear of a ligament, the tough band that holds bones together at a joint.

sputumMucus and other material coughed up from the lungs and lower airways.

squamous cell carcinomaA cancer that starts in squamous cells, the thin, flat cells of the skin's outer layer and the linings of some organs.

stagingWorking out how large a cancer is and how far it has spread in the body.

stasisA slowing or stopping of the normal flow of a body fluid.

stem cellAn unspecialized cell that can divide to make more of itself and develop into specialized cells.

STEMIST-elevation myocardial infarction: a heart attack in which the ECG shows a raised ST segment.

stenosisNarrowing of a passage or opening in the body, such as a blood vessel, heart valve or the spinal canal.

sternumThe breastbone: the flat bone in the middle of the front of the chest.

steroidA fat-based chemical built from cholesterol; the group includes hormones such as cortisol and estrogen, and many drugs.

Stevens-Johnson syndromeA rare, severe reaction, most often to a drug, in which the skin and the moist linings of the body blister and peel away.

stillbirthThe death of a fetus in the uterus at 20 weeks of pregnancy or later.

stimulationSomething that rouses a nerve, organ or person to act or respond, or the act of rousing it.

stoolSolid waste passed from the bowel through the anus; also called feces.

stranger anxietyFear and distress an infant shows around people they do not know.